Roadway



A. SCHMID 2,020,083

ROADWAY Nov. 5, 1935.

Filed June 9, 1953 P [Ml flllorney.

Patented Nov. 5, 1935 ATENT OFFICE ROADWAY Anton Schmid,Deggendorf-on-the-Danube,

Germany 1 Application June 9, 1933, Serial No. 675,055 In Germany February 25, 1932 4 Claims.

Experience has shown that the water content of the ground depends mainly on the changes of temperature. The temperature particularly influences the binding soils, which possess a capillary attraction, such as clay, loam, small-grained sand and similar substances. The hygroscopic power of the soil increases with falling temperatures and diminishes at rising temperatures. It follows therefore, that every change of temperature involves a rearrangement of the moisture of the ground. Frost lifts considerable quantities of moisture from the subsoil and transforms it into ice. Thawing of the ice takes place, as is known, in a downward direction in the same manner as freezing, the water resulting from the melting of the ice collects on the surface because the'layer of ice below the surface prevents the trickling of the water in a downward direction by gravity. The water accumulated at the surface gradually transforms the ballast layer of the roadway right down to freezing depth into a more or less soft and even pulpy mass, which gives way to traffic loads and causes a change of the shape of the roadway.

If a waterproof layer sloping towards the sides of the roadway is inserted intothe construction at lowest freezing depth in order to prevent moisture from rising from the subsoil into the road construction material, a large portion of the moisture emanating from the subsoil is actually held off the roadway and the use of binding materials, (clay, loam, fine-grained sand etc.) as ballast is made possible.

The moisture introduced between the top layer during the construction of the roadway and the waterproof layer moves upwards and downwards under the influence of the temperature, as was shown above, and thus influences the load-resisting qualities of the roadway until this moisture has completely vanished from the roadway. The evaporation of the water contained in the roadway, however, takes place very slowly, especially where a rather impermeable top layer. is used and evaporation is only possible through the sides, so that it may take years before stable conditions are. established.

An accelerated drying of a roadway, which is insulated against rising moisture by means of a watertight layer as before mentioned with consequent quick transformation of the road material into an air-dried mass, renders all those materials, which have hitherto been avoided for road construction because of their sensitiveness to frost, such as clay, loam etc., most desirable for road construction owing to, their quality of hardening after drying.

The method as described below demonstrates how the object of this invention can be quickly achieved. The accompanying drawing shows an 5 example how the invention can be worked.

The figure is an elevational cross sectional view of a road embodying my invention. 4

Referring more particularly to the drawing, l represents the top layer of the roadway, which can be made completely waterproof or be tightened by suitable ballast in such a manner that an accumulation of water on the undersurface of the top layer can take place by condensation only; 2 represents the common ballast (clay, loam, sand or similar materials) between the waterproof and airtight top layer I and the waterand air-tight bottom layer 3. The waterproof bottom layer 3 also closes the sides of the roadway in a waterproof and air-tight manner. 4 is a perforated conduit (stones etc.) which is suitably inclined and arranged at the lowest point of the waterproof layer. 5 are lateral branch lines, which take the water away as it collects at certain times in the conduit 4; the lateral branch line 5 can be connected with a cesspool 6 with ventilation, where it is not practicable to let it simply discharge into the open.

The manner in which the invention as set forth in the drawing acts is as follows: Increase of temperature of the soil and also increase of atmospheric pressure, as has been proven by experiment, cause a decrease of the hydroscopic power of the soil with the result that the moisture introduced into the road material during construction of the roads is freed and flows in a downward direction. As the top surfaces of roadways are made impermeable, and the side slopes and the bottom of the whole road construction are lined with a waterproof and airtight layer, the pressure of the air trapped within said linings is increased at rising temperatures and expands towards the point of least resistance, namely the drain conduit 4, and presses the freed water into the conduit 4.

At falling temperatures the volume of the air contained in the roadway is reduced and fresh air enters through the lateral branches 5 and fills up the spaces which were formerly filled with the water, which had been removed. The more air enters the body of the roadway insulated in the above manner, the more the evaporation is accelerated, the above-said processes repeat themselves almost daily during the greater part of the year.

It is obvious that my method of road building creates conditions in the roadway, which lead in a short time to a complete drying and hardening of the insulated road body, because it is impossible that new moisture enter from below.

Having thus described my invention and the manner in which the same is to be worked, what I now apply to have protected by Letters Patent is as follows:

1 Road construction comprising a roadbody, an airand. watertight sealing coat completely enclosing said roadbody, a drainage disposed within said sealing coat, and conduits penetrating said sealing coat and connecting said drainage with the outside and adapted to conduct water collected in said drainage and damp air to the outside and atmospheric air into said roadbody through said conduits and drainage.

2. Road construction comprising a roadbody, an airand watertight sealing coat completely enclosing said roadbody, said roadbody having a lowermost point, a drainage disposed within said sealing coat and at said lowermost point, and a plurality of conduits penetrating said sealing coat and connecting said drainage with the outside and adapted to conduit the water collected in said drainage and damp air to the outside and atmospheric air into said roadbed from the outside through said drainage.

3. Road construction comprising a roadbody, an airand watertight sealing coat completely enclosing said roadbody, and conduits penetrating said sealing coat and connecting said roadbody with the outside and adapted to conduct water collected in said roadbody and damp air 'to the outside and atmospheric air into said roadbody through said conduits.

4. Road construction comprising a roadbody reaching below the freezing depth of the ground in which said body is laid, an airand watertight sealing coat completely enclosing said roadbody, and conduits penetrating said sealing coat and connecting said roadbody with the outside and adapted to conduct water collected in said roadbody and damp air to the outside and atmospheric air into said roadbody through said conduits.

ANTON SCHMID. 

